Low application temperature hot melt adhesive for cigarette preparation

ABSTRACT

A cigarette filter, process to manufacture, wherein a low application temperature ethylene copolymer based hot melt adhesive is applied to porous and/or nonporous plugwrap paper. As used herein, low application temperatures are temperature between 200° F. and 300° F. (93° C. and 149° C.), preferably, 240° F. to 275° F. (115° C. to 135° C.).

BACKGROUND OF THE INVENTION

[0001] The present invention is directed to the use of low applicationtemperature hot melt adhesive for cigarette filters. Specifically, thehot melt adhesives of the present invention are used to bond filter wrapseam and to anchor the filter element in place on the rod.

[0002] A standard filter tipped cigarette is produced by three differentoperations: (1) filter or plug manufacture, (2) rod manufacture, and (3)tipping.

[0003] The cigarette rod consists of a stream of tobacco wrapped in apaper tube, the paper tube being glued along one longitudinal edge orsurface with a suitable adhesive. This operation takes place at speedsvarying from 2,000 to 16,000 cigarettes per minute. The weight of thecigarette rod, diameter, and length are all closely monitored for bothcost control and tax purposes.

[0004] The filter making operation is similar in many respects to therod manufacture, but the materials and manufacturing equipment used aredifferent. Tobacco smoke filters are most commonly manufactured from acrimped textile tow of cellulose acetate fibers. The tow is then warmedand rolled to produce a material about 9″ wide, and containing an evendistribution of fibers. The tow is “bloomed” in a known manner toseparate the fibers, and a high boiling point solvent, commonly called a“plasticizer”, i.e., triacetin, is applied by spraying, wicking, orother suitable means. The treated tow is then pulled into a cylindricalform and wrapped with paper. During an interval of time, which can beaccelerated by heating, the plasticizer first partially dissolves thesurface of the fibers causing them to become sticky and to bond togetherat points of contact with each other. The plasticizer then migrates intothe fiber leaving the surface dry, but the fibers still remain bonded.

[0005] The bloomed tow is then formed into a tube, and wrapped in paperor plugwrap, the paper being glued along one longitudinal edge. Beforethe paper meets the tow material, adhesive is applied to the center andthe edge forming the anchor and the seam. During this process, heaterbars are used to extend the open time of the adhesive as it meets thetow. The formed filter rod is then passed under chiller plates to setthe adhesive. This is necessary as the filter is immediately cut intosmaller pieces.

[0006] In some applications, such as multi-component or charcoal typefilters, a hot melt adhesive is pre-applied onto filter paper and thenheat sealed by the filter making machine.

[0007] In conventional cigarette filter manufacture, a hot meltadhesive, applied at 350° F. (177° C.), is used for the seam and asecond, aqueous adhesive, is used for the anchor. An aqueous adhesive ischosen with triacetin resistance. Because of the nature of the tow,there is a high degree of radial stress upon the glued bond, so anyadhesive used must be able to stick almost instantly and hold duringstorage and use. This has led to the use of hot melt type adhesives,which by formulation are fast setting, and allow very high machinespeeds to be used.

[0008] Currently polyethylene and ethylene vinyl acetate based hot meltadhesives are used for this filter or plugwrap application. These arepreferred since they are relatively non-polar and resist thedeteriorative effects of triacetin, the most commonly used plasticizer,which often migrates acting as a solvent for the adhesive causing bonddeterioration.

[0009] Most commercially available adhesives used in cigarettemanufacture are either hot melts which require temperatures of 350° F.(177° C.) or are aqueous to provide triacetin resistance.

[0010] However there are problems associated with use of conventionalhot melt adhesives, which are applied at elevated temperatures, usually350° F. These high temperatures increase the operator's risks withrespect both to burns and to inhalation of residual volatiles. Inaddition, the high temperatures require more energy, placing greaterdemands on the manufacturing facility. The higher temperatures can alsocause premature wear and tear on the application equipment i.e.,nozzles, hoses and reservoir tanks.

[0011] The present invention uses low application temperature hot meltadhesives, which can be applied at temperatures in the range 200 to 300°F. (93° C. to 149° C.). The advantages of using such lower temperaturesinclude reduced number of heater elements required in the adhesivereservoir, reduced volatile emissions, and reduced risk of injury andreduced wear and tear on the application equipment. The use of lowtemperature hot melt adhesives may also eliminate the need for use ofboth an aqueous and hot melt adhesive, since some of the hot meltadhesives of the present invention exhibit excellent triacetinresistance. Further, the lower temperatures reduce temperatures in thereactivation section of the machinery and eliminate the need for coolingplates. In addition, the hot melt adhesives of the present inventionhave a fast set speed, low bleed through, improved cuttability and arecomparable or better than 350° F. hot melt adhesives in terms oftriacetin resistance.

SUMMARY OF THE INVENTION

[0012] It has been found in accordance with the present invention, thatlow application temperature ethylene copolymer based hot melt adhesivesprovide unexpected advantages in cigarette filter manufacture.

DESCRIPTION OF THE INVENTION

[0013] The present invention is directed to the use of hot melt adhesivecompositions, which can be applied at temperatures between 200 to 300°F. (93° C. to 149° C.), in the manufacture of cigarette filters. Inparticular, the present invention is directed to a process of makingcigarette filters, and to cigarette filters, wherein a low applicationtemperature ethylene copolymer based hot melt adhesive is applied to atleast one longitudinal edge or surface of porous and/or non-porous plugwrap paper. The adhesives of the present invention are also applicableto multi-component filters or other filters which are prepared bypreapplying the hot melt to filter paper, then heating the coated paperon the filter making machine. As used herein, low applicationtemperatures are temperature between 200° F. and 300° F. (93° C. and149° C.), preferably, 240° F. to 275° F. (115° C. to 135° C.).

[0014] The present invention is directed to the process, and tocigarette filters, which comprise any hot melt adhesive which can beapplied at temperatures between 200 and 300° F. (93° C. and 149° C.).Adhesives suitable for use herein include the hot melt adhesivesprepared from ethylene, ethylene n-butyl acrylate copolymers,ethylene/α-olefin copolymers, and ethylene vinyl acetate copolymers.

[0015] I. Ethylene n-Butyl Acrylate Based Hot Melt Adhesives.

[0016] The ethylene n-butyl acrylate copolymers (EnBA) useful herein arethose containing at least about 10 to 40 weight percent n-butyl acrylateand having a melt index of at least about 40 dg/min, preferably at leastabout 400 dg/min. The preferred copolymers are available from Exxonunder the designation XW 23-AH and comprise approximately 33 to 37weight percent n-butyl acrylate by weight and have a melt index of about400 dg/min. The amount of the copolymer present in the adhesive variesfrom about 5 to 45 weight percent by weight, preferably about 10 to 40weight percent by weight.

[0017] Mixtures of EnBA copolymers may also be used as long as theresultant mixture falls within the described ranges of percent n-butylacrylate by weight, and melt index. It is therefore possible to mix twoethylene n-butyl acrylate copolymers having different melt indices anddifferent percentages of n-butyl acrylate. In a preferred embodiment,the EnBA copolymers described above may be used alone or as a blend withan EnBA copolymer having a melt index of 40 dg/min.

[0018] In addition to the components described above, the adhesivecompositions of the present invention may optionally comprise a secondEnBA copolymer, specifically one containing about 30 to 35, preferably33 weight percent by weight of n-butyl acrylate and having a melt indexof about 6 to 40 dg/min. The preferred copolymers are available from ElfAutochem under the designation LOTRYL 35BA40 and contain approximately35 weight percent n-butyl acrylate by weight and have a melt index ofabout 40 dg/min. The amount of this copolymer present in the adhesivevaries from about 1 to 25 weight percent by weight, preferably 5 to 20%by weight.

[0019] The present invention also contemplates the addition to theadhesive of a polymeric additive selected from the group consisting ofethylene methyl acrylate polymers containing 10 to 28 weight percent byweight methyl acrylate, ethylene acrylic acid copolymers having an acidnumber of 25 to 150, methyl (meth)acrylate copolymers, polyethylene,polypropylene, poly(butene-1-co-ethylene) polymers and low molecularweight and/or low melt index ethylene n-butyl acrylate copolymers. Whensuch additive is present, it is present in amounts up to about 15 weightpercent by weight of composition.

[0020] Tackifying resins useful in the EnBA adhesives of the inventioninclude the aliphatic, aromatic or mixed aliphatic-aromatic hydrocarbonresins, and hydrogenated derivatives thereof, and terpenes and terpenederivatives having a Ring and Ball softening point of between about 70°C. and about 150° C. One skilled in the art would recognize that thesetackifying resins are available with differing levels of hydrogenation.

[0021] Also included are the thermoplastic hydrocarbon resin having aRing and Ball softening point below 130° C., preferably below 120° C.Representative resins include those derived from styrene,alpha-methylstyrene, and/or vinyltoluene, and polymers, copolymers andterpolymers of styrene, alpha-methylstyrene and/or vinyltoluene.Preferred is KRYSTALEX® 3085, a low molecular weight thermoplastichydrocarbon polymer derived largely from alpha-methylstyrene which has aRing and Ball softening point of 85° C. and is available from HerculesInc.

[0022] The thermoplastic hydrocarbon resins are present in the adhesivecompositions of the present invention in an amount of 10 to 60 weightpercent by weight of the composition, preferably 20 to 40 weightpercent.

[0023] The adhesive of the present invention may comprise one or moretackifying resins. For example, an adhesive may comprise ∝-methylstyrene, or ∝-methyl styrene and vinyl toluene.

[0024] Other useful tackifying resins include those sold under thetradenames EASTOAC from Eastman Chemical Company, which are partiallyhydrogenated cycloaliphatic petroleum hydrocarbon resin, ESCOREZavailable from Exxon Chemical Company, which is also a partiallyhydrogenated cycloaliphatic petroleum hydrocarbon resin, WINGTACK whichis an aliphatic, aromatic petroleum hydrocarbon resin available fromGoodyear Chemicals, HERCOLITE which is a partially hydrogenatedcycloalipbatic petroleum hydrocarbon resin available from Hercules,ZONATAC which is a styrenated terpene hydrocarbon resin, made fromd-limonene and available from Arizona Chemical.

[0025] Waxes may be usefully employed in the adhesive compositions ofthe present invention. Waxes are commonly used to modify the viscosityand reduce tack at concentrations up to 60% by weight, preferably lessthan about 45% by weight. Waxes useful in the adhesives of the presentinvention include paraffin waxes, microcrystalline waxes,Fischer-Tropsch, polyethylene and by-products of polyethylene whereinM_(w) is less than 3000. More preferably, the concentration of wax isless than 35% by weight for high melt point waxes.

[0026] Paraffin waxes suitable for use in the present invention includethose having melting points in the range of about 130 to 200° F. (54° C.to 193° C.), such as, for example, PACEMAKER from Citgo, and R-2540 fromMoore and Munger; and low melting point synthetic microcrystalline orFischer-Tropsch waxes having a melting point of less than about 180° C.The most preferred wax is paraffin wax with a melting point of 150° C.

[0027] The adhesives of the invention preferably also contain astabilizer or antioxidant. Among the applicable stabilizers orantioxidants included herein are high molecular weight hindered phenolsand multifunctional phenols such as sulfur and phosphorous-containingphenol. Hindered phenols are well known to those skilled in the art andmay be characterized as phenolic compounds which also contain stericallybulky radicals in close proximity to the phenolic hydroxyl groupthereof. In particular, tertiary butyl groups generally are substitutedonto the benzene ring in at least one of the ortho positions relative tothe phenolic hydroxy group. The presence of these sterically bulkysubstituted radicals in the vicinity of the hydroxyl group serves toretard its stretching frequency, and correspondingly, its reactivity;this hindrance thus providing the phenolic compound with its stabilizingproperties. Representative hindered phenols include; 1,3,5-trimethyl2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl)benzene; pentaerythrityltetrakis-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate;4,4′-methylenebis (2,6-tert-butylphenol); 4,4′-thiobis(6-tert-butyl-o-cresol); 2,6-di-tertbutylphenol;6-(4-hydroxyphenoxy)-2,4-bis(n-octyl-thio)-1,3,5 triazine;di-n-octylthio)ehtyl 3,5-di-tert-butyl-4-hydroxy-benzoate; and sorbitolhexa[3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate].

[0028] Commercially available antioxidants include the hindered phenolsknown as IRGANOX, and available from Ciba-Geigy.

[0029] The performance of these antioxidants may be further enhanced byutilizing, in conjunction therewith known synergists such, for example,as thiodipropionate esters and phosphites, particularly useful isdistearylthiodipropionate. These stabilizers, if used, are generallypresent in amounts of about 0.1 to 1.5 weight percent, preferably 0.25to 1.0%. Other additives such as plasticizers, pigments, dyestuffsconventionally added to hot melt adhesives for various end usescontemplated as well as small amounts of additional tackifiers and/orwaxes such as paraffin wax may also be incorporated in minor amounts,i.e., up to about 10% by weight, into the formulations of the presentinvention.

[0030] The adhesive compositions are prepared by blending the componentsin the melt at a temperature of about 121° C. until a homogeneous blendis obtained, approximately two hours. Various methods of blending areknown to the art and any method that produces a homogeneous blend issatisfactory.

[0031] The resulting adhesives are characterized by viscosity less thanabout 4000 cps at 135° C. They may be applied at temperatures of 121° C.to 135° C. to provide superior adhesive bonds even when exposed to widevariety of temperature conditions. The adhesives possess excellent heatstability as characterized by the 260 hour 121° C. thermal stabilitytest, with no signs of char, skinning or gel formation.

[0032] A preferred formulation for a hot melt adhesive prepared fromEnBA copolymers is one comprising 15 to 45%, preferably 15 to 25%,ethylene n-butyl acrylate copolymers having a melt index of at least 200dg/min, preferably at least about 300, 25 to 55%, preferably 30 to 40%,α-methyl styrene tackifying resins and 15 to 40%, preferably 25 to 35%of a low melting point paraffin wax which can be applied at temperaturesof 225 to 275° F. (107° C. to 135° C.). Another preferred formulationwill comprise 20% of an EnBA copolymer with a melt index of 300 dg/minand 10% of an EnBA copolymer with a melt index of 40 dg/min.

[0033] II. Ethylene α-Olefin Based Hot Melt Adhesives

[0034] Another embodiment of the present invention is directed to hotmelt adhesives prepared from:

[0035] a) 20 to 40 parts ethylene/alpha olefin polymer;

[0036] b) 20 to 40 parts tackifier; and

[0037] c) 10 to 40 parts wax.

[0038] Ethylene/alpha olefin polymers useful herein are those having acomposition distribution breath index greater than 50%, and Mw/Mn lessthan 6. In another embodiment the ethylene/alpha olefin polymers willhave a melt index of 40 to 1000 dg/min, a melt point of 71 to 90° C., adensity of 0.850 to 0.92, a composition distribution breath indexgreater than 50%, and Mw/Mn less than 6. Preferably, the ethylene/alphaolefin polymers will have a melt index of 50 to 500 dg/min and a densityof 0.885 to 0.90. The ethylene/alpha olefin polymers may be copolymersof ethylene and any alpha olefin, for example butene.

[0039] As used herein, composition distribution index, or short chainbranching distribution index, refers to the weight percent of polymermolecules having a comonomer content within 50% of the median totalcomonomer content.

[0040] Tackifiers useful in the present invention include aliphatic orcycloaliphatic hydrocarbons, aromatic hydrocarbons, aromaticallymodified aliphatic or cycloaliphatic hydrocarbons and mixtures thereof.EASTOTAC H100, a hydrogenated cyclopentadiene-based tackifier with asoftening point of 100° C. is the most preferred tackifier.

[0041] Other tackifiers useful herein include polyterpenes, aromaticmodified terpene, and combinations thereof. Also included are thehydrogenated derivatives of modified terpene resins. An example of acommercially available styreneated polyterpene is ZONATAC 105L which hasa Ring and Ball softening point of about 105° C. and is available fromArizona Chemical Company.

[0042] The preferred tackifiers of the present invention are thosehaving a softening point of 90 to 150° C. The present inventioncontemplates that the adhesive composition of the present inventioncomprise one or more of the above adhesive promoting tackifying resins.

[0043] Waxes suitable for use in the present invention include the lowmelting point synthetic paraffin waxes or polyethylene type waxescharacterized by a melting point of about 130 to 200° F. (54° C. to 93°C.). The most preferred wax is PACEMAKER from Citgo.

[0044] The adhesives of the present invention may also contain astabilizer or antioxidant. Among the applicable stabilizers orantioxidants included herein are high molecular weight hindered phenolsand multifunctional phenols such as sulfur and phosphorous-containingphenol. Hindered phenols are well known to those skilled in the art andmay be characterized as phenolic compounds which also contain stericallybulky radicals in close proximity to the phenolic hydroxyl groupthereof. In particular, tertiary butyl groups generally are substitutedonto the benzene ring in at least one of the ortho positions relative tothe phenolic hydroxyl group. The presence of these sterically bulkysubstituted radicals in the vicinity of the deprotonated hydroxyl groupserves to retard its stretching frequency, and correspondingly, itsreactivity; this hindrance thus providing the phenolic compound with itsstabilizing properties. Representative hindered phenols include;1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-benzene;pentaerythrityltetrakis-3(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate;n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate;4,4′-methylenebis (2,6-tert-butyl-phenol); 4,4′-thiobis(6-tert-butyl-o-cresol); 2,6-di-tertbutylphenol;6-(4-hydroxyphenoxy)-2,4bis (n-octyl-thio)-1,3,5 triazine;di-n-octylthio)ethyl 3,5-di-tert-butyl-4-hydroxy-benzoate; sorbitolhexa[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionate] and2,6-ditertbutyl 4-methylphenol (“BHT”). An example of a commerciallyavailable antioxidant is IRGANOX 1010, a hindered phenol, available fromCiba Geigy.

[0045] The performance of these antioxidants may be further enhanced byutilizing, in conjunction therewith, known synergists such as, forexample, thiodipropionate esters and phosphites.Distearylthiodipropionate is particularly useful. These stabilizers, ifused, are generally present in amounts of about 0.1 to 1.5 weightpercent, preferably 0.25 to 1.0 weight percent.

[0046] The present invention also contemplates the addition to theadhesive of a polymeric additive selected from the group consisting ofethylene methyl acrylate polymers containing 10 to 28 weight percent byweight methyl acrylate, ethylene acrylic acid copolymers having an acidnumber of 25 to 150, polyethylene, polypropylene,poly(butene-1-co-ethylene) polymers, ethylene n-butyl acrylatecopolymers and ethylene vinyl acetate copolymers. When such additive ispresent, it is present in amounts up to about 15 weight percent byweight of composition.

[0047] Depending on the contemplated end uses of the adhesives, otheradditives such as plasticizers, pigments and dyestuffs conventionallyadded to hot melt adhesives may be included. In addition, small amountsof additional tackifiers and/or waxes such as microcrystalline waxes,hydrogenated castor oil, amide waxes and vinyl acetate-modifiedsynthetic waxes may also be incorporated in minor amounts, i.e., up toabout 10 weight percent by weight, into the formulations of the presentinvention.

[0048] A preferred embodiment of the present invention is directed to ahot melt adhesive composition comprising:

[0049] a) 0.5% IRGANOX 1010;

[0050] b) 30% of an ethylene/∝-olefin copolymer having a compositiondistribution breath index greater than 50%, and Mw/Mn less than 6;

[0051] c) 35% paraffin wax; and

[0052] d) 35% EASTOTAC H100, 100° C. partially hydrogenatedcyclopentadiene.

[0053] III. Ethylene Vinyl Acetate Based Hot Melt Adhesives

[0054] The ethylene vinyl acetate copolymers (EVA) useful herein arethose containing at least about 15 to 45 weight percent by weight vinylacetate and having a melt index of at least about 6 dg/min, preferablyat least about 400 dg/min. The EVA copolymers will preferably compriseless than 40 weight percent vinyl acetate (VA), most preferably 28% VA.The preferred copolymers are available from Exxon under the designationUL 7710 and comprise approximately 28 weight percent vinyl acetate byweight and have a melt index of about 400 dg/min. The amount of thecopolymer present in the adhesive varies from about 5 to 45 weightpercent by weight, preferably about 10 to 40 weight percent by weight.

[0055] Mixtures of ethylene vinyl acetate copolymers may also be used aslong as the resultant mixture falls within the described ranges ofpercent vinyl acetate by weight, and melt index. It is thereforepossible to mix two ethylene vinyl acetates having different meltindices and different percentages of vinyl acetate. These copolymers areuseful in the range from about 20% to about 50% by weight in theadhesive, preferably from about 25% to about 40%.

[0056] In addition to the components described above, the adhesivecompositions of the present invention may optionally comprise a secondEVA copolymer, specifically one containing about 28 weight percent byweight of vinyl acetate and having a melt index of about 6 to 40 dg/min.The preferred copolymers are available from Exxon under the designationESCORENE UL 7740 and contain approximately 28 weight percent vinylacetate by weight and have a melt index of about 40 dg/min. The amountof this copolymer present in the adhesive varies from about 1 to 25weight percent by weight, preferably 5 to 20% by weight.

[0057] The present invention also contemplates the addition to theadhesive of a polymeric additive selected from the group consisting ofethylene methyl acrylate polymers containing 10 to 28 weight percent byweight methyl acrylate, ethylene acrylic acid copolymers having an acidnumber of 25 to 150, methyl (meth)acrylate copolymers, polyethylene,polypropylene, poly(butene-1-co-ethylene) polymers and low molecularweight and/or low melt index ethylene n-butyl acrylate copolymers. Whensuch additive is present, it is present in amounts up to about 15 weightpercent by weight of composition.

[0058] The adhesives of the present invention preferably also contain astabilizer or antioxidant. Among the applicable stabilizers orantioxidants include those discussed above in connection with theethylene n-butyl acrylate copolymer based adhesives.

[0059] The adhesive may optionally comprise an organic phosphoric acidester selected from the group consisting of tricresyl phosphate,tri-isopropyl phenyl phosphate, tributyl phosphate, triethyl phosphate,trimethyl phosphate, trioctyl phosphate or diphenyl phosphate.

[0060] The ethylene vinyl acetate based adhesive also comprisetackifiers and wax. The tackifiers and wax for use herein are the sameas those described above for use with ethylene n-butyl acrylate basedcopolymer based adhesives. Preferably the tackifier is KRYSTALEX® 3085,a low molecular weight thermoplastic hydrocarbon polymer derived largelyfrom alpha-methylstyrene which has a Ring and Ball softening point of85° C. and is available from Hercules Inc. The preferred wax is paraffinwax with a melting point of 150° C.

[0061] Depending on the contemplated end uses of the adhesives, otheradditives such as plasticizers, pigments and dyestuffs conventionallyadded to hot melt adhesives may be included. In addition, small amountsof additional tackifiers and/or waxes such as microcrystalline waxes,hydrogenated castor oil and vinyl acetate modified synthetic waxes mayalso be incorporated in minor amounts, i.e., up to about 10 weightpercent by weight, into the formulations of the present invention.

[0062] IV. Polyethylene

[0063] The polyethylene polymers useful in this embodiment are thosehaving a melt index of about 5000 to 2000 at 190° C. The polymers willhave a Ring and Ball softening point of 110° C. or less and a density ofabout 0.900 to 0.930. A preferred polymer is EPOLENE C10 from EastmanChemical which has a melt index of 2,250, a Ring and Ball softeningpoint of 104° C., and a density of 0.906. The amount of the polymerpresent in the adhesive will vary from 30 to 60% by weight, preferably50% by weight. In addition, small amounts of additional polymers may beincluded.

[0064] The tackifying resins useful in these adhesive compositions arethe aliphatic or mixed aliphatic aromatic resins such as the terpenes,and styrenated terpenes. Preferred is ECR 179G from Exxon which has aRing and Ball softening point of 90° C.

[0065] The polyethylene adhesives also include a paraffin ormicrocrystalline wax with a Ring and Ball softening point of 130 to 200°F. such as, for example, MICROSERE 599 form IGI Bolder which as a Balland Ring of 195° F. The wax component is utilized at levels of 0 to 30%by weight, preferably 10% by weight, of the adhesive. Other optionalwaxes may be included in small amounts.

[0066] The polyethylene adhesives may also include an antioxidant, suchas those described above in Section II above.

[0067] The adhesive compositions of the present invention are preparedby blending the components in the melt at a temperature of about 121° C.until a homogeneous blend is obtained, approximately two hours. Variousmethods of blending are known in the art and any method that produces ahomogeneous blend is satisfactory.

[0068] The resulting adhesives are characterized by a viscosity lessthan about 3000 cps at 135° C. They may be applied at temperatures of200 to 300° F. (930° C. to 149° C.) to provide superior adhesive bondseven when exposed to a wide variety of temperature conditions. Theadhesives possess excellent heat stability as characterized by the 260hour 250° F. (121° C.) thermal stability test, which shows no signs ofchar, skinning or gel formation. In fact some formulations show thermalstability up to 400 hours at 250° F. (121° C.)

[0069] V. Blends

[0070] The present invention also contemplates that the adhesives may bea blend of any of the above described polymers or copolymers. Forexample, the base polymer in the adhesive may be a blend of EnBA and EVApolymers. Other blends include polyethylene and EVA blends, and polyα-olefin and EVA blends. These and any other combination of polymerscould be used as the base adhesive, with the additional ingredientschosen according to the polymers selected.

[0071] VI. Preferred Embodiments

[0072] Any hot melt adhesive which can be applied at the relativelylower temperatures below 300° F. can be used in the present inventionwherein a low application temperature adhesive is applied to at leastone longitudinal edge of porous and/or non porous plug wrap paper. Onemost preferred embodiment of an adhesive for the present invention is anadhesive consisting of:

[0073] a) 31 parts paraffin wax with a softening point of 150° F.;

[0074] b) 21 parts ethylene vinyl acetate copolymer with a melt index of400 and a vinyl acetate content of 28%;

[0075] c) 11 parts or ethylene vinyl acetate copolymer with a melt indexof 43 and a vinyl acetate content of 28%;

[0076] d) 37 parts of alpha-methyl styrene tackifying resins; and

[0077] e) 0.5 parts of an antioxidant stabilizer.

[0078] Another preferred example of a hot melt adhesive usable in thepresent invention is an adhesive comprising:

[0079] a) 50 parts polyethylene such as EPOLENE C-10 from EastmanChemicals;

[0080] b) 40 parts of an aliphatic-aromatic hydrocarbon tackifyingresin;

[0081] c) 10 parts of a microcrystalline wax with a softening point of195° F. such as MICROSERE 5999; and

[0082] d) 0.2 parts of an antioxidant stabilizer such as LOWINOX (BHT)from Great Lakes Chemicals.

[0083] The resultant adhesives are characterized by viscosities of lessthan about 5000 cps at 121° C., a Ring and Ball softening point of about80° C. to about 115° C., fiber tearing bonds on plugwrap paper in therange of about 0° F. to about 120° F. (−18° C. to 51° C.).

[0084] The following examples are merely exemplary, and not intended tolimit the scope of the present invention in any manner.

EXAMPLES

[0085] In the following examples, which are provided for illustrativepurposes only, all parts are by weight and all temperatures in degreesCelsius unless otherwise noted.

[0086] In the examples, all adhesive formulations were prepared insingle blade miser heated to 135° C. by blending the components untilhomogeneous.

[0087] The adhesives were then subjected to various tests simulating theproperties needed for successful commercial applications.

[0088] Melt viscosities of the hot melt adhesives were determined on aBrookfield Model RVT Thermosel viscometer using a number 27 spindle.

[0089] Test specimens for determining elevated temperature peel andshear strengths were prepared as follows: an adhesive bead was appliedat 121° C. to a strip of 50 pound Kraft paper 1 inch wide by 3 incheslong across the width of the paper. A second piece of Kraft paper of thesame dimensions was immediately placed over the first piece and 200 gramweight placed on top of the composite construction. The compressedadhesive bead width was ½ inch.

[0090] Elevated temperature peel and elevated temperature shear weredetermined by attaching a 100 gram weight to each specimen and placingthe specimens in a forced-draft oven. The temperature was raised in 5.5°C. (10° F.) increments from 38° C. the specimens remained at a giventemperature for 15 minutes for conditioning. The heating cycle was rununtil the final bond failed. Each peel and shear specimen was preparedand tested in duplicate. The elevated peel and shear value shown is theaverage temperature of failure for the two bonds. In some cases, thesample failed as the temperature was being adjusted within the 10°increments and is noted as such.

[0091] Adhesion at various temperatures, as noted, was determined byapplying a ¼ inch wide bead of adhesive widthwise to a 2 inch by 3 inchpiece of non porous plug wrap paper and immediately bringing a secondpiece of paper into contact. The bond is aged at each temperature for 24hours. The bonds were separated by hand and a determination of theamount of fiber tear (FT) was noted.

[0092] Bleed through was measured using porous plug wrap paper. Thistest is done to measure staining of the paper by the adhesive. Six 2×1″sheets of plug wrap paper were stacked. An adhesive bead, ¼″ wide wasapplied between the center two sheets, and aged at 110° F. (43° C.) for24 hours. The bleed of the adhesive to the top and bottom sheets wasnoted.

[0093] Open time/set time was measured on a automated bond tester usinga 0.04″uncompressed bead applied to corrugated single-walled 65 lb. Opentime measures that amount of time the product can remain open, i.e.,achieve 100% fiber tear, with ten seconds compression time. Set time isthe amount of time necessary to compress and achieve 100% fiber tearwith 1 second open time.

[0094] Triacetin resistance was measured after soaking the adhesive bondfor 24 hours in triacetin.

Example 1

[0095] In this example, conventional plug wrap adhesives were comparedto the low application temperature adhesives of the present invention.Comparative Samples A and B are conventional plugwrap adhesives whichare applied at 350° F. (177° C.). Samples 1-4 are in accordance with thepresent invention, and are applied at 250° F. (121° C.). Theformulations of the adhesives studied are shown below:

[0096] Sample A: is a commercially available EVA based hot melt adhesivefrom National Starch and Chemical Company under the designation 34-2760.

[0097] Sample B: is a commercially available EVA based hot melt adhesivefrom National Starch and Chemical Company under the designation 34-2757.Sample 1: Amount (% by weight) Hindered phenol (antioxidant) 0.5Paraffin wax 150° F. 31 ESCORENE UL 7710 21 (EVA, MI 400 dg/min, 28% VA)ESCORENE UL 7740 11 (EVA, MI 40 dg/min, 28% VA) KRISTALEX 3085 37(α-methyl styrene, 85° C.) Sample 2: BHT (antioxidant) 0.5 EPOLENE C10,104° C. 50 (polyethylene polymer) ECR 179G 40 (hydrocarbon resin)microcrystalline wax. 195° F. 10 Sample 3: Hindered phenol (antioxidant)0.5 Paraffin wax, 150° C. 31 EXXON XW 23-AH 21 (EnBA, 33% BA, MI 300dg/min) ELF AUTOCHEM 35BA40 11 (EnBA, 33% BA, MI 40 dg/min) KRISTALEX3085 37 (α-methyl styrene, 85° C.) Sample 4: Hindered phenol(antioxidant) 0.5 Paraffin wax, 150° C. 35 Polyalpha olefin 30 EASTOTACH100-R, 100° C. 35

[0098] The results are shown below in Table 1: TABLE 1 Sample A Sample BSample 1 Sample 2 Sample 3 Sample 4 Viscosity @ appl ˜4400 cps ˜2735 cps˜2390 cps ˜3600 cps ˜3025 cps ˜2820 cps Adhesion @ appl temperature RT100, 50% 100, 50% 100% 100% 100% 100% 40° 100% 100% 100% 100% 100% 100%100° 100% 75, 50% 100% 100% 100% 100% Bleed Slight Slight Very SlightVery Slight Slight Slight through @ 100° F. Triacetin 0% Fiber 25% Fiber0% Fiber 80% Fiber 0% Fiber 0% Fiber resistance 24 hrs. Tear Tear TearTear Tear Peel/Shear Adj 130°/ Adj 130°/ 110°/150° F. Adj 110°/ Adj100°/ Adj 100°/ Adj 190° F. Adj 190° F. 190° F. 150° F. Adj 150° F.Stability 260 hrs. @ 350° F. @ 350° F. @ 250° F. @250° F. @250° F. CharV. Slight None None None None None ER None None None None None NoneOther None SI. Hazy None None St. None Delta visc. |51.0% −24.0% 1.4%13.3% Separation 2.1% −0.9% 04″ bead width @appl 1.7 secs 1.0 secs 2.0secs 4.0 secs 1.5 secs 2.0 secs Temp Open Time with 10 sec compressionSet Time with 1 sec open time Partial FT = 1.3 Partial FT = 4.0 PartialFT = 0.7 Partial FT = 0.7 Partial FT = 1.5 Partial FT = 2.0 secs secssecs secs secs secs Full FT = 3.3 Full FT = NA Full FT = 2.0 Full FT =1.1 Full FT = 6.0 Full FT = 4.3 secs secs secs secs secs

[0099] The results in Table 1 above, show that the low applicationtemperature adhesives, Samples 1, 2, 3 and 4, have good adhesioncomparable to the conventional adhesives. Samples 1 and 2 are superiorin bleed through, and have good thermal stability. The large viscositychange observed with Samples A and B at 260 hours indicates that theseadhesives are not stable; the EVA is degrading. Sample 2 shows excellentfiber tear even after 24 hours of exposure to triacetin.

[0100] A significant difference between the adhesives of the presentinvention and conventional adhesives is that the adhesives of thepresent invention have a long open time and a fast set time allowing forwet out and quick set prior to the cutting step of the cigarette makingprocess.

What is claimed is:
 1. A cigarette filter comprising a low application temperature ethylene copolymer based hot melt adhesive.
 2. A cigarette filter according to claim 1 wherein the adhesive is applied at 200 to 300° F. (93° C. to 149° C.).
 3. A cigarette filter according to claim 1 wherein the adhesive comprises ethylene n-butyl acrylate copolymer comprising 10 to 40 weight percent n-butyl acrylate with a melt index of at least 40 dg/min.
 4. A cigarette filter according to claim 3 additionally comprising a second ethylene n-butyl acrylate copolymer, wherein the second ethylene n-butyl acrylate copolymer comprises 25 to 35 weight percent n-butyl acrylate.
 5. A cigarette filter according to claim 4 wherein the second ethylene n-butyl acrylate copolymer has a melt index of 40 dg/min and comprises 35% ethylene n-butyl acrylate.
 6. A cigarette filter according to claim 1 wherein the adhesive comprises: a) 10 to 40 weight percent ethylene n-butyl acrylate comprising 10 to 40 weight percent n-butyl acrylate with a melt index of at least 400 dg/min; b) 10 to 60 weight percent tackifier; c) 0 to 35 weight percent wax; and d) optionally 1 to 25 weight percent of a second ethylene n-butyl acrylate, wherein the second ethylene n-butyl acrylate comprises 33 to 35 weight percent butyl acrylate with a melt index of 40 dg/min.
 7. A cigarette filter according to claim 6 wherein the adhesive comprises: a) 15 to 45% ethylene n-butyl acrylate copolymers having a melt index of at least 200; b) 25 to 55% α-methyl styrene tackifying resins; and c) 15 to 40% of a low melting point paraffin wax.
 8. A cigarette filter according to claim 6 additionally comprising a polymeric additive selected from the group consisting of ethylene methyl acrylate polymers containing 10 to 28 weight percent by weight methyl acrylate, ethylene acrylic acid copolymers having an acid number of 25 to 150, methyl (meth)acrylate copolymers, polyethylene, polypropylene, poly(butene-1-co-ethylene) polymers and low molecular weight and/or low melt index ethylene n-butyl acrylate copolymers, and combinations thereof.
 9. A cigarette filter according to claim 1 wherein the adhesive comprises: a) from 20 to 40 weight percent of an ethylene/α-olefin copolymer; b) from 20 to 40 weight percent tackifier; and c) from 10 to 40 weight percent wax.
 10. A cigarette filter according to claim 9 wherein the ethylene/α-olefin copolymer has a composition distribution breath index greater than 50%, and Mw/Mn less than
 6. 11. A cigarette filter according to claim 9 wherein the ethylene/α-olefin copolymer has a melt index of 40 to 1000 dg/min, a melt point of 71 to 90° C., a density of 0.850 to 0.92, a composition distribution breath index greater than 50%, and Mw/Mn less than
 6. 12. A cigarette filter according to claim 9 additionally comprising polymeric additive selected from the group consisting of ethylene methyl acrylate polymers containing 10 to 28 weight percent by weight methyl acrylate, ethylene acrylic acid copolymers having an acid number of 25 to 150, polyethylene, polypropylene, poly(butene-1-co-ethylene) polymers, ethylene n-butyl acrylate copolymers and ethylene vinyl acetate copolymers, and combinations thereof.
 13. A cigarette filter according to claim 1 wherein the adhesive comprises ethylene vinyl acetate comprising 5 to 45 weight percent vinyl acetate with a melt index of at least 400 dg/min.
 14. A cigarette filter according to claim 13 additionally comprising a second ethylene vinyl acetate copolymer, wherein the second ethylene vinyl acetate copolymer comprises 28 weight percent vinyl acetate with a melt index of 6 to 40 dg/min.
 15. A cigarette filter according to claim 13 additionally comprising a polymeric additive selected from the group consisting of ethylene methyl acrylate polymers containing 10 to 28 weight percent by weight methyl acrylate, ethylene acrylic acid copolymers having an acid number of 25 to 150, methyl (meth)acrylate copolymers, polyethylene, polypropylene, poly(butene-1-co-ethylene) polymers and low molecular weight and/or low melt index ethylene n-butyl acrylate copolymers, and combinations thereof.
 16. A cigarette filter according to claim 1 wherein the adhesive comprises 30 to 60 weight percent polyethylene polymer with melt index of 5000 to 2000 dg/min at 190° C., a density of 0.900 to 0.930, and a softening point less than 110° C.
 17. A cigarette filter according to claim 1 wherein the adhesive comprises blends selected from the group consisting of blends of EnBA and EVA polymers; blends of polyethylene and EVA; blends of poly α-olefin and EVA; and combinations thereof.
 18. A cigarette filter according to claim 1 wherein the hot melt adhesive comprises: a) 31 parts paraffin wax with a softening point of 150° F.; b) 21 parts ethylene vinyl acetate copolymer with a melt index of 400 and a vinyl acetate content of 28%; c) 11 parts or ethylene vinyl acetate copolymer with a melt index of 43 and a vinyl acetate content of 28%; d) 37 parts of alpha-methyl styrene tackifying resins; and e) 0.5 parts of an antioxidant stabilizer.
 19. A cigarette filter according to claim 1 wherein the hot melt adhesive comprises: a) 50 parts polyethylene; b) 40 parts of an aliphatic-aromatic hydrocarbon tackifying resin; c) 10 parts of a microcrystalline wax with a softening point of 195° F.; and d) 0.2 parts of an antioxidant stabilizer.
 20. The process for preparing a cigarette filter comprising applying a low application temperature ethylene copolymer based hot melt adhesive to porous and/or nonporous plugwrap paper.
 21. The process according to claim 20 wherein the adhesive is applied at 200 to 300° F. (93° C. to 149° C.).
 22. The process according to claim 20 wherein the adhesive comprises ethylene n-butyl acrylate copolymer comprising 10 to 40 weight percent n-butyl acrylate with a melt index of at least 40 dg/min, and optionally a second ethylene n-butyl acrylate copolymer, wherein the second ethylene n-butyl acrylate copolymer comprises 25 to 35 weight percent n-butyl acrylate.
 23. The process according to claim 20 wherein the adhesive comprises: a) 10 to 40 weight percent ethylene n-butyl acrylate comprising 10 to 40 weight percent n-butyl acrylate with a melt index of at least 400 dg/min; b) 10 to 60 weight percent tackifier; c) 0 to 35 weight percent wax; and d) optionally 1 to 25 weight percent of a second ethylene n-butyl acrylate, wherein the second ethylene n-butyl acrylate comprises 33 to 35 weight percent n-butyl acrylate with a melt index of 40 dg/min.
 24. The process according to claim 20 wherein the adhesive comprises: a) 15 to 45% ethylene n-butyl acrylate copolymers having a melt index of at least 200; b) 25 to 55% α-methyl styrene tackifying resins; and c) 15 to 40% of a low melting point paraffin wax.
 25. The process according to claim 20 wherein the adhesive comprises: a) from 20 to 40 weight percent of an ethylene/α-olefin copolymer; b) from 20 to 40 weight percent tackifier; and c) from 10 to 40 weight percent wax.
 26. The process according to claim 25 wherein the ethylene/α-olefin copolymer has a composition distribution breath index greater than 50% and Mw/Mn less than
 6. 27. The process according to claim 25 wherein the ethylene/α-olefin copolymer has a melt index of 40 to 1000 dg/min, a melt point of 71 to 90° C., a density of 0.850 to 0.92, a composition distribution breath index greater than 50%, and Mw/Mn less than
 6. 28. The process according to claim 20 wherein the adhesive comprises ethylene vinyl acetate comprising 5 to 45 weight percent vinyl acetate with a melt index of at least 400 dg/min.
 29. The process according to claim 20 wherein the adhesive comprises 30 to 60 weight percent polyethylene polymer with melt index of 5000 to 2000 dg/min at 190° C., a density of 0.900 to 0.930, and a softening point less than 110° C.
 30. The process according to claim 20 wherein the adhesive comprises blends selected from the group consisting of blends of EnBA and EVA polymers; blends of polyethylene and EVA; blends of poly α-olefin and EVA; and combinations thereof.
 31. The process according to claim 20 wherein the adhesive comprises: a) 31 parts paraffin wax with a softening point of 150° F.; b) 21 parts ethylene vinyl acetate copolymer with a melt index of 400 and a vinyl acetate content of 28%; c) 11 parts or ethylene vinyl acetate copolymer with a melt index of 43 and a vinyl acetate content of 28%; d) 37 parts of alpha-methyl styrene tackifying resins; and e) 0.5 parts of an antioxidant stabilizer.
 32. The process according to claim 20 wherein the adhesive comprises: a) 50 parts polyethylene; b) 40 parts of an aliphatic-aromatic hydrocarbon tackifying resin; c) 10 parts of a microcrystalline wax with a softening point of 195° F.; and d) 0.2 parts of an antioxidant stabilizer. 